Continuous di-electric heating of electrically non-conductive material



y 1967 L. PUNGS ETAL 3,322,928 CONTINUOUS DI-ELECTRIC HEATING OFELECTRICALL NON-CONDUCTIVE MATERIAL I Original Filed Sept. 1 i959 2 Sheets -shet 1 Fly. I 52 37 1 k; '1 I 4 w I a zzzz 5 5/ Im emws LEO PUNGSKURT LAMBERTS BERND GRIESBACH e ngamw AGT 1967 1.. PUNGS ETAL 3,322,928

CONTINUOUS DI-ELECTRIC HEATING OF ELECTRICALLY NON-'CONDUCTIVE MATERIALOriginal Filed Sept. 1, 1959 2 Sheets-Sheet 2 Jnvenfor'g 4 LEO PUNGSKURT IAMBERTS BERND GRIESBAC United States Patent 5 Claims. c1.219 10.s3

This case No. 327,569 is a division of No. 837,554 filed Sept. 1, 1959now Patent No. 3,109,080.

Various methods and devices have become known, which serve for theheating of electrically non-conductive substances, particularly for thepurpose of interwelding the same. The heating of the workpieces iseffected either by contact heating or by a high frequency field,frequencies up to 6O 10 cycles per second being used.

Heretofore, the electrodes serving for the heating of the workpieces bymeans of an electric field as well as for applying, if desired, thepressure required for the welding, have been made either as spot weldingelectrodes having an axial movement or in the form of rollers having arotational movement. The high frequencyenergy has been supplied throughsimple cable leads connected to the eectrodes and opposite electrodes,if desired, through earth. Such arrangements can be used withoutdifficulty on the high frequency side, as long as the workingfrequencies lie within a range for which the dimensions of the electrodesystem and of the driving members are small as compared with the wavelength, so that the electric phenomena within the welding arrangementmay be considered as quasi-stationary.

For substances having a comparatively high loss factor and not too higha welding temperature, the frequency required for an interwelding or adeformation lies within the said range, so that the known arrangementscan be used.

Substances having a low loss factor, in particular fabrics made ofthermoplastic synthetic fibres or even mixed fabrics, and substanceshaving a comparatively high welding temperature cannot, however, befaultlessly welded at working frequencies up to 60x10 cycles per second,since the heating attainable with the substances and fabrics does notsufiice'for interwelding.

For the interwelding of the aforesaid substances accordingly high andvery high frequencies are required, which lie in the range above 60 10cycles per second up to some 1000 10 cycles per second. Thesefrequencies correspond to wave lengths from 5 m. to about 10 cm. Theknown heating devices, however, are no longer suitable for these wavelengths since their dimensions are of the same order of magnitude asthese wave lengths and the arrangement can no longer be considered asquasistationary. The supply of electric energy to the point of weldingwould be completely indeterminate and no heating sufficient forinterwelding would occur. Moreover, a considerable proportion of theenergy would be lost through radiation.

The principal object of the invention is to provide a method for thedielectric heating of non-conductive substances, particularly for thepurposeof welding, in electric fields of high and very high frequency,which allows to interweld faultlessly even substances having -a low lossfactor, particularly fabrics of thermoplastic synthetic fibres andsubstances having comparatively high welding temperatures. A furtherobject of the invention consists in providing devices for carrying outthe said method which allow to adjust the optimum conditions for thesup- 3,322,923 Patented May 30, 1967 ICC ply of energy and its deliveryto the point of heating or welding, and wherein the delivery of energyis controllable and adjustable in spite of the conditions no longerbeing quasi-stationary. There devices are moreover intended to have theadvantage of minimum radiation losses into space, which is particularlyimportant in view of suppression of interference. Finally they aim atthe advantage of permitting the interwelding of substances which are notweldable by the methods hitherto known.

It has become known for the purpose of as uniform as possible adi-electric heating of stationary bodies of comparatively largedimensions (such as motor car tyres and the like) to arrange thesebodies between the layers of a condenser and to include this condenserinto a co-axial conductor system, one layer being connected to the innerconductor, and the. other to the outer one. Such a method is, however,unsuitable for the heatin and interwelding of continuously movingmaterials, particularly of foils and fabrics. Here it is not the uniformheating of a comparatively large body that matters, but on the contrarythe heating and accordingly the electric field has to be concentrated inthe shape of a point or se-am. Moreover the workpieces have to be movedon between the electrodes.

The invention solves the problems set to it in that the high frequencyenergy is supplied in a manner known in itself through a co-axialconductor system or through a screened double conductor systemsymmetrical to earth, and that through a gap in the inner conductor orinner conductor system between the two mutually juxtaposed small facesof the gap a strong electric field concentrated on this area isgenerated for the pointor seam-shaped heating or interwelding of theworkpieces, the workpieces to be welded being moved through the field ina corresponding slot in the outer conductor or in the screening,respectively.

The concentration of the electric field on the faces of the gap in theinner conductor is attained in the co-axial system by a conductorsection which is connected in series with the capacitance of the gap andtunable by means of a short-circuiting slide, which section is soadjusted that the voltage and the electric field in the gap assume thevalues most favourable for the welding.-

In a double conductor system symmetrical to earth the concentration ofthe field in the gap is attained by arranging ahead of said gapappropriately dimensioned inductances in both conductors of the system.

The device according to the invention for carrying out this method maybe so constructed that the electrodes themselves form the innerconductor of a co-axial system, which is interrupted at the points ofheating, and which is enclosed by a co-axial outer conductor likewiseinterrupted at the point of heating, so that the workpiece can be passedthrough this gap which forms a capacitive short circuit for the workingfrequency.

In another embodiment the electrodes may, however, be so constructedthat they themselves form parts of a conductor system symmetrical toearth. Then the common screening is interrupted at the heating point bya gap for passing the workpiece to be heated through it, which gap actsas a short circuit for the working frequency.

The electrodes forming the inner conductor or parts thereof may bedesigned as roller electrodes.

The adjustmentand tuning-member included in the co-axial conductorsystem for adjusting the high frequency output at the heating point isestablished in that a second oo-axial conductor system is formed by asecond co-axial tubular conductor section of suitable diameter andlength pushed over the outer conductor of the co-axial conductor system.Its effective length may be varied by a shortcircuiting slide.

The adjustmentand tuning-member included into the co-axial conductorsystem for adjusting the high frequency output at the point of heatingmay alternatively be established by providing a second conductor sectionco-axial with the inner conductor of the co-axial conductor system andformed by a reduction of the diameter of the conductor and by acorresponding length of a tubular conductor surrounding the reducedinner conductor, the effective length of said tubular conductor beingmade variable by means of a short-circuiting slide.

The gap provided in the outer conductor or in the screening envelopethereof for passing through it the workpiece to be heated is providedwith flanges or plane faces in order to increase its bridgingcapacitance.

The invention is illustrated in the drawings by way of example invarious embodiments. In the drawings:

FIG. 1 is a section of an embodiment having roller electrodes;

FIG. 2 is an embodiment of a screened parallel conductor arrangementhaving roller electrodes, illustrated diagrammatically;

FIG. 3 shows a device having a divided working condenser in a doubleconnector system symmetrical to earth, and

FIG. 4 shows a coaxial conductor system having a divided workingcondenser.

In the embodiment of FIG. 1 the possibility of structural application ofthe principle of the invention is shown when using roller electrodes.

Two roller electrodes 37, 38 are mounted on insulating roller bodies 39,40 which are fixed on drive shafts 41, 42. The supply of the highfrequency energy is effected through the co-axial cable having an outerconductor and an inner conductor 43. The source of energy is a highfrequency generator 43'. In alignment with the axle 42 of the roller 40lies a co-axial conductor having an outer conductor 46 and an innerconductor 44 as a tuning system. The tuning itself is effected through ashort-circuiting slide 44. The outer conductors 45, 46 are enlarged inthe form of capsule-shaped metal casings 47, 48 which enclose the rollerbodies 39, 40 and electrodes 37, 38 except for a narrow gap 49. Byflange-shaped extensions 50, 51 the capacitive closing of the outerconductors 45, 46 through the gap 49 is improved. The inner conductor52, 53 is enlarged by the rims of the roller electrodes 37, 38. Theconnections of the roller electrodes 37, 38 to the inner conductors 52,53 and to the tuning system is effected by means of capacitive couplings54, 55.

In this manner a homogeneous and defined co-axial system, which isclosed outwardly, is formed also in the embodiment just described.

Although the coaxial system has substantial advantages because of thesimpler structural fittings of the electrodes into the conductors andbecause of dispensing with symmetry, one may yet use in principle alsothe symmetrical parallel conductor system, preferably with cylindricalscreening, which permits likewise to attain positively defined voltageconditions at the point of heating, provided correct symmetry andcorresponding adaptations are made.

As an example of the application of a screened symmetrical parallelconductor system in the sense of the invention, an arrangement havingroller electrodes is diagrammatically illustrated in FIG. 2. To theroller electrodes 56, 57 supply leads 58, 59 are connected into whichinductances 58', 59' are inserted which serve for tuning the system.These inductances 58', 59' may be adjustable. In many cases they mayhowever be built in fixedly when appropriately dimensioned.

The whole system is surrounded by a cylindrical screening 63, whichencloses the rollers 56, 57 in an enlargement 64 wherein a working slot64' is provided.

The illustration is made merely diagrammatically in order to explain theprinciple. In practice the leads are coupled capacitively to therollers, in order to dispense with slip rings.

For the simultaneous production of two weld seams lying at a spacingparallel to one another in a device of the kind described hereinabovethe working condenser may be subdivided into two working condensers.This may be effected in that an electrically conductive element isinserted into the gap between the electrodes.

In FIG. 3 such an arrangement is illustrated for a screened doubleconductor system symmetrical to earth. On a common shaft two rollers 81,82 are here mounted, which are insulated from one another and to whichthe conductors 83, 84 are connected through tuning inductances 85, 86.The screening envelope is denoted 87. Opposite the rollers 81, 82 liesan electrically conductive plate 88, which may lie on earth. The gapsbetween the rollers 81 and 82, respectively, and the plate 88 form thepart-working condensers, by the aid of which the welding is carried out.As in the other embodiments described hereinabove, the rollers apply apressure in the direction of the field, so that heating and pressureoccur on the same point of the material.

This arrangement safeguards absolute freedom from interference even whenthe two working condensers are unequally loaded, for example when thenumbers of layers of material at the two welding points are unequal.

In FIG. 4 a design similar to that of FIG. 3 is illustrated, however fora coaxial conductor system. The supply of energy is here effectedthrough the co-axial conductors 90. At the end of the inner conductor 91again a roller 92 is arranged, which is mounted on a common shaft with aroller 93 in the tuning portion 94 of the system. The rollers are againinsulated from one another. The tuning is effected by a short-circuitingslide 95. The inner conductor 96 of the tuning portion is connected tothe roller 93.

Opposite the rollers 92, 93 again an electrically conductive plate 97 isarranged. Here, too, the fields effecting the welding are formed betweenthe rollers 92 and 93, respectively, and the plate 97, namelyperpendicular to the plate 97.

The plate 97 of the design according to FIG. 4, as by the way also theplate 88 of the design according to FIG. 3, need not necessarily be aplane plate; on the contrary the welding fields may be made to lie at anangle to one another by an appropriate formation of the plate andarrangement of the rollers.

As will be seen in FIGS. 3 and 4, the ends of both conductors (i.e. theelectrodes) may lie on the same side of the said electrically conductiveelement. The latter may form the working table, if desired.

While we have described herein and illustrated in the accompanyingdrawings what may be considered typical and particularly usefulembodiments of our said invention, we wish to be understood that we donot limit ourselves to the particular details and dimensions describedand illustrated; for obvious modifications will occur to a personskilled in the art.

What we claim as our invention and desire to secure by Letters Patent,is:

1. In a device for the continuous dielectric heating and interwelding ofprogressively moved electrically nonconductive material, in combinationwith a source of high frequency electric energy of at least 60x10c.p.s., a coaxial high frequency conductor system connected to saidsource, which conductor system comprises two inner conductors, tworoller electrodes each terminating one of said inner conductors andhaving contacting edges adapted to form a gap when the non-conductivematerial is inserted therebetween thereby including between one anothersaid working condenser, two outer conductors co-axially surrounding saidinner conductors and roller electrodes, respectively, and includingbetween one another a slot in alignment with the said gap of the innerconductors, and tuning element means included in the co 5 axialconductor system and being in series with the working condenser in saidsystem, one of the inner conductors and the associated outer conductorbeing connected to said source of high frequency energy.

2. A device as claimed in claim 1, comprising flangeshaped enlargementsof the said two outer conductors adjacent the said slot increasing thebridging-over capacitance thereof.

3. In a device for the continuous dielectric heating and interwelding ofprogressively moved electrically nonconductive material, in combinationwith a source of high frequency electric energy of at least 60 10 c.p.s,a coaxial high frequency conductor system connected to said source,which conductor system comprises two inner conductors, two rollerelectrodes each terminating one of said inner conductors; electricallyconductive plate means disposed in spaced relation with said rollerelectrodes for forming the working condensers therebetween, two outerconductors co-axially surrounding said inner conductors and rollerelectrodes, respectively, and spaced from said electrically conductiveplate means, one of the inner conductors and the associated outerconductor being connected to said source of high frequency energy, andtuning mean-s included in the co-axial conductor system in associationwith the other of the inner conductors and its associated outerconductor.

4. The device of claim 3 wherein said roller electrodes are disposed inside-by-side relation and are oriented perpendicularly relative to theelectrically conductive plate means to produce electrical fields normalto the plate means.

5. The apparatus of claim 3 wherein said roller electrodes are disposedin side-by-side relation and are oriented to define an included angletherebetween being out of normal relative to the said electricallyconductive plate means thereby producing electrical fields in angular relation with the plate means.

References Cited UNITED STATES PATENTS 2,465,102 3/1949 Joy 21910.532,468,263 4/1949 Joy 219-10.53 X 2,569,717 11/1950 Wenger 21910.53 X2,569,968 10/1951 Autie et a1. 21910.53 X 3,109,080 10/1963 Pungs et al.21910.53

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner.

1. IN A DEVICE FOR THE CONTINUOUS DIELECTRIC HEATING AND INTERWELDING OFPROGRESSIVELY MOVED ELECTRICALLY NONCONDUCTIVE MATERIAL, IN COMBINATIONWITH A SOURCE OF HIGH FREQUENCY ELECTRIC ENERGY OF AT LEAST 60X106C.P.S., A COAXIAL HIGH FREQUENCY CONDUCTOR SYSTEM CONNECTED TO SAIDSOURCE, WHICH CONDUCTOR SYSTEM COMPRISES TWO INNER CONDUCTORS, TWOROLLER ELECTRODES EACH TERMINATING ONE OF SAID INNER CONDUCTORS ANDHAVING CONTACTING EDGES ADAPTED TO FORM A GAP WHEN THE NON-CONDUCTIVEMATERIAL IS INSERTED THEREBETWEEN THEREBY INCLUDING BETWEEN ONE ANOTHERSAID WORKING CONDENSER, TWO OUTER CONDUCTORS CO-AXIALLY SURROUNDING SAIDINNER CONDUCTORS AND ROLLER ELECTRODES, RESPECTIVELY, AND INCLUDINGBETWEEN ONE ANOTHER A SLOT IN ALIGNMENT WITH THE SAID GAP OF THE INNERCONDUCTORS, AND TUNING ELEMENT MEANS INCLUDED IN THE COAXIAL CONDUCTORSYSTEM AND BEING IN SERIES WITH THE WORKING CONDENSER IN SAID SYSTEM,ONE OF THE INNER CONDUCTORS AND THE ASSOCIATED OUTER CONDUCTOR BEINGCONNECTED TO SAID SOURCE OF HIGH FREQUENCY ENERGY.